In an interview with TV Line, Arrow executive producer Wendy Mericle spoke about how Curtis will be incorporated into Team Arrow in season 5, now that Kellum is a series regular, and how his role compares to that of Felicity:

“Essentially, if she’s software, he’s hardware. As he evolves into becoming Mr. Terrific in Season 5, one of the things we’re really exploring is differentiating them by having Curtis be more like Cisco on The Flash. We want him to be a bit more hands-on, a little more about building physical tech.”

On The Flash, Cisco Ramon (Carlos Valdes) was a mechanical engineer for STAR Labs before the particle accelerator explosion, while his partner Caitlin Snow (Danielle Panabaker) was a bio-engineer. Of the two, Cisco generally builds the gadgetry needed for Barry (Grant Gustin) - and sometimes for the heroes on Arrow as well - but Caitlin largely handles the biological aspects of superheroics, like discovering and treating the speed-related disease killing Hunter Zolomon (Teddy Sears) in The Flash season 2.

So, according to Mericle's statement, it sounds as if Curtis' season 5 role will follow Cisco's in that he will handle the gadgets (and, perhaps, the suit upgrade Amell teased for Oliver next season) so that Arrow doesn't need to provide an explanatory line of dialogue crediting Cisco's work when new tech is introduced to the series. It seems this storyline will also work to help develop Curtis into his own superhero, Mr. Terrific, similarly to how Cisco has slowly developed his alter ego, Vibe, with the tech he has created and discovered through his work with metahumans.

Still, one of the criticisms of The Flash is the lack of story for Caitlin, who spent much of season 2 either dealing with the death of Ronnie Raymond (Robbie Amell) or her relationship with Hunter. Since Felicity has long been a fan-favorite character on Arrow, it's unlikely viewers would respond positively to her season 5 storyline should it be pushed aside for more inclusion of Curtis. That being said, there are many new characters joining Arrow for season 5, and since it remains to be seen whether Thea and Diggle will pick their weapons back up, there may be plenty of room on Team Arrow for all the characters to explore their respective story threads.

The Flash season 3 will premiere Tuesday October 4th at 8pm on The CW, Arrow season 5 will premiere in the same timeslot on Wednesday October 5th, Supergirl season 2 on Monday October 10th, and Legends of Tomorrow season 2 on Thursday October 13th.